Comment by Night_Thastus

That is an exceptional outlier. It's almost entirely (>90%) made up of one religious group that has strict cultural rules about early marriage and having many children.

That's not something typical outside of that one particular group, nor can you copy-paste that anywhere else.

I think in fact it's the opposite. Because of how universal below-replacement rates are in EVERY developed nation, it shows just how independent it is from factors of culture, economics, environment, etc. It takes a seriously unusual situation like the one in Kiryas Joel for below-replacement to not be the norm.